Pressure sensors equipped with micromechanical sensor elements are used today in machine manufacturing, process technology, automotive engineering, and in medical technology for many diverse measuring tasks. Differential-pressure sensors are used for comparing pressures that prevail in spaces or media that are separated from one another. The media to be measured can be liquids, gases or also vapors.
In automotive engineering, a typical application of micromechanical differential-pressure sensors is to compare the exhaust back pressure upstream and downstream of the particulate filter. Since, in this connection, very high absolute pressures occur, and the exhaust gases create a harsh particle-laden measuring environment, ever greater demands are placed on the dynamics and ruggedness of the sensor element in terms of its micromechanical structure, but also its signal acquisition.
One approach for determining differential pressure provides for recording the two measurement pressures to be mutually compared using two independent absolute pressure sensors and then for calculating the difference between the thus obtained measured values. For the most part, however, this method does not yield accurate enough results in practice. The reason for this is that the measuring accuracy of the generally available absolute-pressure measuring devices is not high enough, particularly in high pressure ranges and/or at high absolute pressures, but at small differential pressures, so that it does not suffice to determine the pressure differential precisely enough.